Z scores and Percentiles

Question 1

What do the Z-score tables give?

Answer 1

the area to the left of a particular z value

Question 2

The area to the left of z is denoted by ___.

Answer 2

A(z)

Question 3

A z score for a data value describes …

Answer 3

the number of standard deviations above or below the mean

Question 4

What does a negative z score indicate?

Answer 4

• the data value is below the mean

- is shown to the left of the mean on the standard normal distribution curve

Question 5

What does a positive z score indicate?

Answer 5

• the data value is above the mean

- is shown to the left of the mean on the standard normal distribution curve

Question 6

The z-score table gives the:

Answer 6

• area under the curve, to the left of the z-score or
• percentage of data to the left of the z-score or
• probability that a randomly chosen data value is to the left of the z-score

Question 7

The mean, median, and mode have a z-score of _____.

Answer 7

zero

Question 8

The table shows that a z score of -1.33 is associated with a shaded area of 0.0918. What does this mean?

Answer 8

• approx 9% of the heights are lower than 170cm

- a height of 170cm would be in the 9th percentile

Question 9

The table shows that a z score of +1.467 is associated with a shaded area of 0.9288. What does this mean?

Answer 9

• approx 93% of the heights are lower than 212cm

- a height of 212cm would be in the 93rd percentile